Seth Shostak debunks the IDist argument that detecting extraterristrial signals is about complexity:

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And yet we still advertise that, were we to find such a signal, we could reasonably conclude that there was intelligence behind it. It sounds as if this strengthens the argument made by the ID proponents. Our sought-after signal is hardly complex, and yet we’re still going to say that we’ve found extraterrestrials. If we can get away with that, why can’t they?

Well, it’s because the credibility of the evidence is not predicated on its complexity. If SETI were to announce that we’re not alone because it had detected a signal, it would be on the basis of artificiality. An endless, sinusoidal signal – a dead simple tone – is not complex; it’s artificial. Such a tone just doesn’t seem to be generated by natural astrophysical processes. In addition, and unlike other radio emissions produced by the cosmos, such a signal is devoid of the appendages and inefficiencies nature always seems to add – for example, DNA’s junk and redundancy.

It's also worth pointing out that the most intensively designed radio signals we've produced so far are almost indistinguishable from noise, as they scatter tiny pulses of energy throughout the spectrum in what are effectively random positions. There are a number of advantages in doing this, one of which is that energy put into coherence is not energy put into information. If you can make your message coherent through other means than self-similarity in the carrier you save big time. That's one of the implications of information theory, by the way, and one way we can tell that whatever the source of biological design is, it isn't up on its Shannon.

The logical conclusion of this is a radio signal that is only detectable if you have an enormous amount of knowledge about it beforehand. Otherwise, it just isn't there.

(The military and chums like this a lot - a case of design being used to hide itself. Does this mean our undetectable biological designer is engaged on a stealth mission, and if we actually detect it we've achieved a measure of parity? Didn't that sort of activity provoke all sorts of trouble in Eden and Babel? I merely ask.)

Assuming we're not the smartest radio engineers in the universe, it is entirely plausible that we could be receiving extremely advanced, extraordinarily highly designed signals all the time and merely be incapable of recognising them as such. I suppose this is a special case of Clarke's Third Law.

There is even a perfectly respectable theory that such evolution is inevitable, and that this means our chances of catching a SETI signal that's not intended as such are even smaller than before -- we'd have to catch it in the tiny window of opportunity between a civilisation inventing radio and refining it beyond continuous wave transmissions. That phase has only lasted a hundred years with us and it's already nearing its end. We're shutting off the huge transmitters that powered analogue TV and radio in preference for far more efficient digital systems, and I can buy a small black box for my computer that gives it the same capabilities as aeronautical radar. The next stage in wireless design - ultrawideband - has the potential to do everything we've done with megawatts in the past, with milliwatts.

All this applied to SETI is a case of scientists using a theory of intelligent design - with input from information theory, no less - to predict how to best deploy resources, in this case towards systems that can best spot deliberate beacons or optical comms which have a higher chance of reception.

You'd think that the IDers would be beside themselves with joy at this, except that the reasons why it works here are exactly the reasons that ID is completely inappropriate for biological systems. We can assume a lot about the capabilities and motivation of the designers -- those assumptions may be wrong: the SETI experiment tests this -- and how those will relate to the artifacts we're looking for. SETI predicts a range of possible outcomes, assigns a loose probability to them, and provides a way of contextualising the results of the experiment.

As the original essay said, 'complexity' is the least part of this. It's about making predictions based on existing information, conducting an experiment and seeing what we find. When intelligent design does this, it's perfectly welcome in science. When it doesn't, it's bollocks.

R

--------------Uncle Joe and Aunty MabelFainted at the breakfast tableChildren, let this be a warningNever do it in the morning -- Ralph Vaughan Williams